Soil: our lives depend on it!

By Becca Smithers

Soil is underrated. It may look like dirty stuff that just holds plants in the ground, but it’s so much more! Soil is a multi-layered, complex system holding nutrients for plants, providing a home for invertebrates and vertebrates, and is the basis of thousands of food chains. Without soil, we wouldn’t be able to grow the crops we need to eat or grow the feed for livestock. Our way of life depends on soil!

CC-BY-SA Nilfanion

CC-BY-SA Nilfanion

2015 is the United Nations International Year of Soil, focusing on protecting and caring for soils so that we can sustain our ever growing global population. By 2050 it is estimated that the global population of humans will exceed 9 billion people, and they will all need food! Our soils are being degraded and lost as we use land for urbanisation, pasture lands for industrial livestock and improper land management. We need to learn to look after our soils.

This blog will look at what makes up soil, why it is so useful to us and why we should care about our soils.

What is soil?

Soil is made up of minerals from rocks, organic matter from plants and animals, and the many species’ living in the soil. Earthworms keep soils clean by digesting the soil and their movement keeps the soil fresh, as do moles. Bacteria in the soil recycle nitrogen and carbon, fungi transport nutrients and help to decompose organic matter. Intricate root systems of plants and trees provide shelter and food for lots of organisms. Soil is a thriving ecosystem!

CC-BY-SA Rob Hille

CC-BY-SA Rob Hille

There are different layers in soil that serve different purposes.Humus is the top layer of soil and is rich in organic matter and nutrients. Top soil lies below and contains humus, which is very nutrient and mineral rich and ideal for plant growth. The next level down is subsoil which is less nutrient rich but contains lots of minerals and some solid rock pieces. Beneath this is weathered rock fragments containing very little organic matter.

Eventually, if you dig down far enough you will reach bedrock; the solid rock that all these soil layers are sitting on.

You can get different types of soil based on the size of the soil grains, the larger the soil grains the muddier the soil when wet. Clay, sand, silt, chalk, peat, and loam soils have different consistencies and allow for growth of different plants. The pH of the soil affects which plants can grow, very acidic or alkaline soils make it difficult for certain plant species to become established.

Why is soil important to us?

Soil is incredibly useful. It acts as a drainage system when it rains to absorb water therefore preventing floods. This drainage also filters water to clean it as minerals and micro-organisms in the soil detoxify the water of pollutants. These processes are referred to as ecosystem services, where natural processes benefit humans.

CC-BY-SA Steve Freeman

CC-BY-SA Steve Freeman

The organic matter in soils contain nutrients which are essential for plant growth, which is incredibly important to us as we need plants to eat! Vegetables, fruits, cereals all need to be grown, as well as crops to be used as feed for animals.

Micro-organisms in the soil convert toxic compounds within the soil into useful nutrients for plants. For example ammonia is converted into nitrogen in the nitrogen cycle. These micro-organisms also decompose organic matter for it to be recycled through the carbon cycle, and are even responsible for that nice earthy smell after it rains which is referred to as petrichor.

Why do we need to look after our soils?

Soil takes a very long time to make. It can take up to 1000 years for just 1 cm of top soil to be produced. With an increasing global population, more demand for urbanisation, and land for food production, we are losing a lot of our fertile land. Many areas of the world rely on farming but their soils are not suitable for growing lots of plants, so there needs to be more of a global effort to protect and make the most of our soils.

If you have a garden you can do your best to treat your soils with care, grow a variety of plants and restrict the amount of chemicals you use. Buying organic produce helps to support the maintenance of high quality soil and other environmental standards.


You can find out what sort of soil you have in your garden by trying out this activity!

Activity: solving soil!

You will need:

  • A glass jar
  • Water softener powder (1 tsp)
  • A watch
  • A marker pen
  • Some soil!

What to do:

  • Fill your jar 2/3 full of water
  • Stir in the teaspoon of water softener powder
  • Fill the jar with soil to just below the top of the jar
  • Put the lid on and shake it for about 20 seconds
  • Set the jar on a table and wait 20 seconds, a dark layer will form on the bottom of the jar. This layer is sand, mark it with your marker.
  • Wait two minutes, the next layer will form and this will be the silt.
  • The final layer to settle will be clay, this can take up to a week to settle.
  • The thickest layer indicates which type of soil you have in your garden. Soils are a combination of different particles.



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Posted in Activity, Biology
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